1. Field of the Invention
This invention relates to a shedding controlling apparatus for a loom for automatically performing a pick finding operation or the like during stopping of the loom wherein each of a plurality of heald frames is driven by a drive motor for the exclusive use without utilizing a crank shaft of the loom as a driving source therefor.
2. Description of the Related Art
A method and an apparatus for a loom wherein each of a plurality of heald frames is driven by a drive motor for the exclusive use without utilizing a crank shaft of the loom as a driving source therefor are already known and disclosed, for example, in Japanese Patent Publication Application No. 63-58940.
Employment of a motor for the exclusive use for driving each of a plurality of heald frames provides an advantage that exchange of mechanical parts such as a cam is not required upon changing of a textile weave or of a shedding pattern (which is shedding stroke pattern of a heald frame in one cycle of a loom, which applies also to the following description) according to a type of a yarn or the like.
Meanwhile, a loom is stopped immediately when, for example, weft insertion fails as seen in FIG. 5. Next, various operations such as a leveling operation (operation of arranging all heald frames to a weft closing position in order to minimize elongation of wefts during stopping of the loom), a pick finding operation (operation of moving a heald frame to a maximum shedding position of a preceding cycle in order to pick up an end of a failed weft into a weft shedding), a starting preparing operation (operation of moving, after removal of the failed weft, the heald frame to a shedding position corresponding to a predetermined starting crank angle of a further preceding cycle) may be required.
With such conventional method and apparatus, during operation of the loom, the amount of rotation of the drive motor is controlled in accordance with a predetermined shedding pattern with respect to a crank angle, and accordingly, a heald frame can be driven maintaining a synchronized relationship with the crank shaft of the loom. So, if a failure in weft insertion occurs and the loom is stopped, then a pick finding operation and so forth can be performed by rotating the crank shaft of the loom reversely. However, by the synchronization between the drive motor and the crank shaft of the loom, a beating operation will be performed during such a pick finding operation, which will cause a weft bar to be produced on a woven fabric, which is not preferable. Thus, in order to eliminate this, it is necessary to cut the synchronized relationship between the drive motor and the crank shaft of the loom and cause only the drive motor to be driven. In this instance, however, upon subsequent re-starting of the loom, an operation for establishing a synchronized relationship between them is required, which, however, is very complicated and cumbersome. Further, if power supply interruption or the like occurs during operation of the loom, and since the amount of inertial rotation is different between the crank shaft of the loom and the drive motor, the synchronized relationship between them cannot be maintained, and consequently, an operation for synchronization is necessary similarly as described above. Particularly, in this instance, since such operation of synchronization is necessary for all looms in the plant, the burden in labor is very heavy.
Further, since a leveling operation, a pick finding operation and a starting preparing operation must individually be performed manually, also there is a problem that operation of the loom is very complicated and requires a high degree of skill.